The present invention relates to a plasma processing apparatus that processes a substrate-like material, such as a semiconductor wafer, arranged in a processing chamber inside a vacuum container by plasma that is formed using microwave supplied into this processing chamber, and to a device that outputs microwave supplied to a processing chamber. In particular, the present invention relates to a plasma processing apparatus and a microwave output device that form microwave using an oscillator, such as a magnetron, and supply the same to a processing chamber.
In the plasma processing apparatus for manufacturing a semiconductor device by processing a substrate-like sample, such as a semiconductor wafer, using plasma, a stable and high precision output of microwave is required. A magnetron is conventionally used for generation of such microwave.
A device for outputting such microwave typically includes a magnetron, a filament power supply for heating a filament of the magnetron, a high voltage power supply for oscillating and exciting the magnetron. However, the output efficiency of a magnetron differs depending on its use condition and furthermore a magnetron also has an individual difference, and therefore in order to obtain a high precision and stable output, a detector for detecting a microwave output is provided on the output side of a magnetron and a microwave output monitor signal obtained by this detector is fed back to a high voltage power supply to control the output of the high voltage power supply, thereby adjusting the magnitude of the output to within a predetermined value range.
As the examples of such a related art, the disclosures in JP-A-01-232727, JP-A-2000-294396, JP-A-2011-103270, and TECHNICAL REPORT OF IEICE SPS 2004-18(2005-02) are known. For example, JP-A-01-232727 discloses a technique for feeding back a signal obtained by monitoring the output of microwave to a high voltage power supply and controlling the output of this high voltage power supply.
JP-A-2000-294396 discloses a technique, wherein in order to realize a high speed response in automatic matching of microwave, a monitor signal is fed back to a high voltage power supply to control the output of the high voltage power supply, and on the other hand when a reflection electric power is high, an anode current monitor signal is temporarily fed back to control the output of the high voltage power supply. JP-A-2011-103270 discloses a technique for detecting the moding of a magnetron from a signal, which is obtained by monitoring an anode current, and controlling the output of a high voltage power supply. TECHNICAL REPORT OF IEICE SPS 2004-18(2005-02) describes an output fluctuation called a parasitic oscillation.